Probably 90% of autos from all manufacturers don't have drain plugs. Some of them are sealed units and don't provide any means of draining or filling the trans with fluid unless you have a special tool.

It's done for two reasons, the main one is so you will have to drop the pan, which means you will need a new gasket, gaskets come with the filter, and that's what they want you to do...change the filter. And while you are in there you will likely wipe off the magnet

The cars with drain plugs typically have a wire mesh filter rather than a paper or fiber one.

The second reason is because shade tree mechanics and occasionally dealers service would accidentally drain the transmission and then add more engine oil to the crankcase.

My father did this to his Volvo a couple decades back, I believe it was the last time he ever worked on a car

It's done for two reasons, the main one is so you will have to drop the pan, which means you will need a new gasket, gaskets come with the filter, and that's what they want you to do...change the filter. And while you are in there you will likely wipe off the magnet

The cars with drain plugs typically have a wire mesh filter rather than a paper or fiber one.

The second reason is because shade tree mechanics and occasionally dealers service would accidentally drain the transmission and then add more engine oil to the crankcase.

My father did this to his Volvo a couple decades back, I believe it was the last time he ever worked on a car

There are some folks on here who shall remain nameless that have drained the wrong one and overfilled the other on other vehicles.

Let's just say their SO was not a happy camper when the dealership pointed out the error after the car was towed in for repair.